Inventory - Summary of Interests in Lot Option Agreements (Details) - Unconsolidated lot option agreements - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Real Estate Properties [Line Items]
Deposits & Non-refundable Pre-acquisition Costs Incurred	$ 78,971	$ 91,854
Remaining Obligation	$ 341,737	$ 408,300

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_RealEstatePropertiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration